Patent GB-435934-A (GB)
Title: Improvements relating to automatic weighing scales
IPC: G01G23/18
Filed: 1934-03-28
Abstract: 435,934. Weighing-apparatus. TOTH, S., 4, Ujpesti Rakpart, Budapest. March 28, 1934, No. 9693. Convention date, March 28, 1933. [Class 143] In an automatic weighing-scale wherein a follower member is driven after a moving part of the weighing scale for the purpose of adjusting an indicating or printing device and the driving motor of the follower is automatically disconnected on reaching the deflection point, means is'provided for retarding the follower member before finally arresting it in a position corresponding to the deflected position of the weighing-scale. As shown in Fig. 1, when the scale pointer 1 has completed its movement and come to rest a switch 17 is manually closed thereby applying a magnetically-operated locking device 14 to the pointer, energizing a magnet 10 to retract a pair of contacts 8, 12, and starting a motor 6 to drive the printing or indicating counter 4 and rotate the follower arm 2. When the follower arm approaches the pointer the contact 12 touches an extended contact 7 and the speed of the follower arm is rapidly reduced by an electromagnetic change speed gear 13. The contact 8 next touches the end of the pointer 1 and the motor is stopped, a locking relay 9 locks the printing discs 4, and a relay 15 raises the printing platen 16 to permit the printing to be effected by manual or electromagnetic means. In a modification, Fig. 2 (not shown), instead of the rotating follower arm 2 a straight rack carries the contacts 8, 12 and is moved by the motor so that the contacts successively engage a spiral of conducting material secured to the spindle of the pointer. In a modification, Fig. 3, the follower arm is controlled by the damping piston 19 of the weighing scale in association with a piston 23 connected to the follower arm. Orifices 22 connect the cylinders of the two pistons. During the follow-up movement of the follower arm the piston 23 is moved downwards by the motor, displacing the fluid through the orifices 22 until these are closed by the presence of the piston 19 after which the movement is retarded by leakage past the piston until an electric contact on the follower automatically stops the motor, the printing counter being driven by the motor as described above. In a modification, Fig. 4, a control arm 26 is moved in accordance with the motion of the pointer 1 and when the pointer is displaced by a load on the scale pan the control arm presses down springs 25 to cut out resistance 24 in the motor circuit. The movement of the pointer opens the contact 8 to de-energize the locking relay 9 and close the motor circuit at the contacts 18. The motor rotates at full speed and drives the follower arm 2 after the pointer. The springs 25 urge the plate 26 towards its middle position and as the pointer oscillates about its balancing position the resistance 24 is cut out to slow down the motor step by step, the contact 28 being operated as necessary, to reverse the drive to the follower through a reversing device 27. When the follower reaches the pointer 1 the relay 9 is operated to stop the motor, and energize a magnet 30 to disconnect the printing counter 4 from the driving shaft 5 by means of a clutch 29. A printed record may then be obtained by pressing a contact button 41. By pulling out a button 43 the type wheels are zeroized and in the zero position notches in the wheels allow a peg 35 to fall and open a switch 33 thereby de-energizing the magnet 30 and again coupling up the clutch 29 to the shaft 5. Two contacts 19, 20 are provided on the follower member to produce a retraction of the follower if a small load, insufficient to close the contact 28, is removed from the scale pan. In a further modification, Fig. 5, the follower member consists of a four-compartmented mercury trough T mounted on parallel motion links, and the co-operating contacts 48 .. 51 are similarly mounted in connection with a load-balancing pendulum 44. The motor 6, locking relay 9 and change speed gear 13 are controlled by the mercury contacts in a manner similar to the control in Fig. 1. In a further modification, Fig. 6 (not shown), the follower carries two photo-electric cells and corresponding lamps. A slotted disc secured to the indicating spindle is interposed between the cells and the lamps, the arrangement being such that the cells come into action successively to retard and stop the follower by means of magnet and motor circuits substantially as described in connection with Fig. 1. In a further modification, Fig. 7, the pointer 1 and the follower 2 carry condenser plates 68, 69 which, according to the extent of overlapping, vary the grid potential and consequently the anode current in an amplifier tube 70. An alternating current supply 72 and a leakage resistance 71 are connected to the grid. The anode current varies the current in one winding x of the adjusting motor 6 in opposition to the other winding y. Thus as the condenser plates overlap to a greater extent and the current in the winding x increases the motor slows down continuously until, when the condenser plates coincide the locking magnet 9 is actuated and the further operations are carried out in the manner previously described. In a further modification, Fig. 8 (not shown), the condenser plates 68, 69 are arranged in one branch of a bridge circuit so that as the condenser plates move into coincidence the voltage across the bridge diminishes and disappears, at the same time affecting the anode currents of two amplifier tubes which respectively retard the follower and operate the locking magnet. In a further modification, Fig. 9, the condenser plates 68, 69 form part of a resonance circuit 78 in the grid circuit of an amplifying tube 70. In the anode circuit are arranged two other resonance circuits 79, 80 tuned to a constant frequency but damped by different resistances, and each back-coupled to the resonance circuit 78 by coils 82, 83. The retarding and locking magnets 13, 9 for the follower are shunted by a resistance 84 in the anode circuit. The arrangement is such that as the condenser plates 68, 69 move towards coincidence self-energization increases the anode circuit and first operates the retarding magnet 13 and finally the locking magnet 9.